Fusing device



Feb. 19, 1952 E. R. sABEL ET AL 2,586,484

FUSING DEVICE med Apr-11 29, 195o 2 SHEETS- SHEET 1 A5 BESTOS COMPOSITION z/ A/q TKAN SITE.

AJ LJ INVENTORS EDWARD R. SABEL FRANK z. GALsnscHT www A'rrolzNsY Feb-19, 1952 E. R. SABEI. ET Al. 2,586,484

FUsING DEVICE Filed April 29, 195o 2 SHEETS- SHEET 2 N :A Nmusouwe: senslsvK (R \j1 l Fig.

CQMPOST'ION, d

e N m INVENTORS EDWARD E. SABEL FRANK I'. GALBRECHT BWM A TTQRNE Y Patented Feb. 19, 1952 FUSING DEVICE Edward R. Sabel and Frank I. Galbrecht, Rochester, N. Y., assignors to The Haloid Company, Rochester, N. Y., a corporation of New York Application April 29, 1950, Serial No. 158,974

3 Claims.

This invention relates to fusing devices, and particularly to devices for fusing powder images on sheets of paper and like material.

The invention has its principal application in the fusing of resinous powder images produced by electrophotography or xerography onto sheets of paper and the like to which the powder images have been transferred after they have been formed by deposition of powder on an electrostatic latent image.

One of the 'important applications of the process of electrophotography or xerography comprises its use in a compact oilice copying machine for general oice use. When such a machine is used, the nal step of the process is to fix a powder image onto a sheet of paper or the like to produce a iinished print. The present invention provides a fusing device which is particularly well suited for cnice use in association with a copying device of the type described.

In order to fuse resinous powder images formed of the resins now commonly used it is necessary to heat the powder and the paper base to which it is to be. fused to a relatively high temperature, such as 325 F. It is undesirable, however, to raise the temperature of the paper substantially higher than 375 F. because of its tendency to turn brown and deteriorate at such elevated temperatures. This imposes rather exacting temperature control requirements on the fusing device and also makes it necessary that the heating be distributed uniformly over the area of the sheet to be treated. A further requirement is that no portion of the heating element which may normally or accidentally come into contact with the sheet being treated shall have a temperature which will damage the sheet.

For oice use it is also important that no part of the unit with which the operator can normally come into contact shall be sufficiently hot to injure the operator.

Other requirements are that the unit shall provide good and rapid heat transfer to the sheet being treated, that it shall have relatively low power consumption when left on for extended periods of time, such as when it is maintained in standby condition, and that the operating temperature shall be adjustable by a serviceman but not readily adjustable by an inexperienced operator. ticularly ease of removal of the completed print from the heating zone, are also of paramount importance.

The present invention contemplates a fuser which satisiies the above requirements and, in addition, is pleasing in appearance, relatively simple in construction and operation, and sufiiciently rugged for normal handling. The fuser comprises a fusing chamber or oven into which the copy to be fused is inserted by a slide, the

Rapidity and ease of operation, and parheat being supplied to the copy by a heated top plate having a temperature which will not injure the copy during fusing of the image. The device also incorporates certain novel features of construction and heat insulation which effectively protect the operator from injury and the copy from damage.

The invention comprises the features of construction, combination of elements, arrangement of parts, and method of operation referred to above or which will be brought out and exemplied in the disclosure hereinafter set forth, including the illustrations in the drawing.

In the drawings:

Figure 1 is a sectional side elevation of a fusing device embodying features of the present invention; y

Figure 2 is a top view thereof with the cover and certain parts removed;

Figure 3 is a perspective view of the copy slide used in the fuser; and

Figure 4 is a perspective view of the complete fuse'r unit.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the construction and arrangement of parts and in the method of operation without departing from the spirit of the invention.' In the following description and in the claims parts will be identified by specic names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Referring to the drawings, the fuser comprises a rectangular box-like metal housing formed of a main body part I0 and a cover I I which fits over the open top of the body part with its side walls telescoping with the side walls of the body. The body I0 is provided with four legs I2 at the corners, the legs conveniently being formed of sheet angle pieces bent at right angles to provide stiifening and to provide a plane surface which is spot welded at I3 to the bottom of the body I0. Legs I2 are also provided with rubber feet I4 in the form of soft rubber washers or grommets riveted to the legs.

At the front end of the fuser unit the end Wall of body I0 is formed into an inturned horizontal iiange I5 located slightly below the middle of the end wall and a pair of inturned side flanges I6 rising vertically from the ends of flange I5. The front end of cover II is also provided with an inturned iiange I1 spaced approximately l inch above flange I5 and parallel to it when the cover is in position on the body I0. Flanges I5, I6 and II together define a slide opening approximately 1 inch in height and of a length suflicient to accommodate a copy slide I8 comprising a rectangular plate. A rectangular inner housing I9 formed of sheet metal is located horizontally within the space enclosed by body I and cover II with the bottom wall thereof substantially at the same height as ange I5, and the side walls substantially in the plane with flanges I6. The rear wall of the inner housing is spaced from the rear end of the body IB. The top of the inner housing com" prises a removable cover plate 2i] located in a plane spaced from cover II but above the plane of flange I'I. A heated plate 2I of heavy sheet metal ismounted within the inner housing with its bottom face slightly below the plane of flange I1. The front end of plate 2I is bent up at right angles at a point spaced inward from the front end of the body I0. its upper edge providing a rest for the front end of cover plate 2l). Plate is provided with a flange 22 slightly spaced from its front end, flange 22 normally resting just inside the upturned front end of heated plate 2I to serve as a positioning element for plate 253. A partition 23 is also provided in the space between plates 28 and 2l approximately one-third of the distance from the rear of the space. The space is thereby divided into two sections. In the front section a plurality of clamp-on type metal-sheathed electric resistance heating elements 24 are clamped to plate 2I by clamping screws 25 to provide good heat transfer contact between the heating elements and heated plate 2 i. A thermostat 2t is clamped to the surface of plate 2I in the space to the rear of partition 23. The thermostat is provided with a temperature adjusting screw 2l and plate 2l] is provided with an opening directly above the head of the screw in order that a screw driver may be inserted for temperature adjustment. A screw driver hole is also provided in cover I I directly above the openM ing in plate 2i), this hole preferably being closed by a snap-on button 28 which can be pried oir to enable insertion of a screw driver for ten1perature adjustment.

The fuser is provided with an electric plug and cord 2S which enters the housing through an opening in the rear wall provided with an insulating grommet 30. An ori-off switch 3l is mounted in the front wall of the fuser as well as a pilot light 32. Heat resistant insulated wires 33 provide the necessary connections between the electric `cord 2S and the switch, pilot light, resistance heating elements and thermostat. The switch is connected to close a circuit through the series arrangement of thermostat 26 and heating elements 2li. While elements 24 will normally be connected in parallel, series connections can, in some cases, be used if desired to change the wattage rating or adjust the heating pattern. Pilot light 32 is connected directly across the input circuit by switch 3I to indicate the on or olf condition of the unit.

It will be noted that wide spacing is provided between the inner housing I9 and the body I0 and also between inner cover plate 20 and outer cover II. This space is filled with a semirigid heat insulating material 34 which may suitably comprise bonded mats of glass ber, asbestos, or other high quality heat insulator. For the best protection the spacing between the inner and outer housings is preferably in excess of l inch on all sides except for the necessary slide opening.

At the slide opening the front edge of the bottom wall of inner housing I9 is secured by round headed rivets 35 to a plate 36 of refractory material of low heat conductivity such as pressed asbestos composition, ceramic or the like. Plate 36 extends underneath ange I5, thereby providing a closure for the gap between the bottom wall of housing I9 and the inneredge of flange I5, and also serving as a locating or positioning member for the front end of the inner housing. A sheet metal iiange 3'1 is spot welded inside the front end wall of cover II and is bent up at an angle of approximately degrees so that its inner edge is positioned slightly above the front edge of plate 2t. The purpose of flange 3l is primarily to prevent particles of the insulating mats 34 from falling down onto the slide I3 and to act as a support for the front ends of mats 34 which line cover II.

Slide I8, which is shown in section in Figure l and in perspective in Figure 3, preferably is formed of a plate of refractory material of low heat conductivity, such as a pressed asbestos composition, known as Transite, or other similar refractory material of low heat conductivity. Slide i8 is slightly wider and longer than the sheets to be treated. At its iront edge slide I8 is provided with a stiiiening and clamping assembly consisting of a rectangular block of simi lar composition St which is clamped against the top face of slide EP3 and a metal channel member 39 which encloses the iront edge of slide IB and block 38, the assembly being held together by screws or rivets. A U-shaped metal strap member 4Q is riveted to the mid-portion of channel 39 and a handle 4I of wood or other material of low heat conductivity is secured to the central part of strap where it is spaced from channel 39. It is apparent that strap 40 not only provides a rugged connection between handle 4I and channel 39 but also, by virtue of its shape, increases the length of the heat path to the handle. The slide is also provided with a sheet lifting device comprising a piece of stiff wire 42 which passes through a hole in channel 39 and block 38. Wire 42 is bent to form a crank lever adjacent to handle 4I and provided with an insulating handle 43. The wire is also bent at two right angles where it rests against the top of slide I8 so that rotation of the crank lever by handle 43 will lift the body portion of the wire away from slide I8 and thereby serve as a lifting device for sheets of paper or other material to aid in removing the fused copies from the hot surface of slide I8. The inner end of slide I is provided with a narrow strip 44 secured to the face of the slide to provide an abutment for 'the sheets being treated and prevent their sliding ofi the rear end of the slide.

In operation, the unit is rst connected to an electric outlet by cord 29 and switch 3l is oper ated to close a circuit through resistance elements 24 in series with thermostat 36. Pilot light 32 is also turned on by this operation. Plate 2I, being of aluminum or other metal of high heat conductivity, is rap'dly heated by elements 24, the heat spreading uniformly to all parts of plate 2 I. By virtue of the grouping of the heating elements 24 near the front end of plate 2I, the greatest amount of heat is supplied at the point of greatest heat loss, namely, the slide slot at the front end of the unit. As there is little heat loss from the rear end of inner housing I9, that portion of plate 2l which extends to the rear of the heating elements soon assumes a temperature substantially the same as that prevailing directly under the elements 24, and once this temperature has been assumed it is constantly maintained because of the small heat loss from the rear end of the inner chamber. Thermostat 25 is shielded by partition 23 against any substantialheatng by hot air convection from elements 24 and is thereby able to exercise control determined primarily by the temperature of plate 2| Once the desired temperature has been reached, thermostat 23 operates to disconnect heating element 24. Due to the effective insulation of the unit, plate 2| then remains at operating temperature for a substantial period of time before further heat needs to be supplied. As plate 2| gradually cools below the temperature for which thermostat 26 has been set, the thermostat will again close the circuit and bring the temperature of plate 2| up to the maximum value of the thermostat range. During the heating period, the air directly over slide |8 is also heated and the surface of slide |8 is raised to a temperature only slightly lower than that of plate 2|.

When fusing temperature has been reached, the unit may be maintained in standby condition with relatively small power input and without danger 'of injuring the top of a desk or other surface on which it is placed.

When the operator desires to fuse a, copy, she simply grasps lhandle 4| and withdraws slide I8 a sufficient distance to permit convenient placing of the copy to be fused on the face of the slide. After the copy is placed in position, slide I8 is pushed into the limit of its travel at which time block 38, together with the slide, effectively closes the slot and prevents circulation of air into or out of the inner chamber. The powder image and surface of the sheet are rapidly heated by radiation from plate 2| and by the hot air atmosphere between plate 2| and slide I8, so that the copy is completely fused in all areas within a few seconds. The operator Will normally estimate the fusing time and, since the heat source (plate 2|) is only slightly hotter than fusing temperature, no damage is encountered by greatly exceeding the normal fusing time. When the operator estimates that the number of seconds have been at least sufficient to insure proper fusing, she withdraws the slide a sufficient distance to expose the entire sheet and depresses handle 43 with her finger or thumb, thereby lifting wire f print is thus removed and the slide reinserted so that block 38 will close the slide slot and prevent excessive loss of heat during standby operation.

It will be apparent that a novel and efcient fusing device for powder images has been described.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is:

1. A uniform temperature fusing device for fusing resinous powder images onto a temperature sensitive sheet material, the powder having a fusing temperature only slightly below the temperature of sensitivity of the sheet material comprising, in combination, a hotplate comprising a metal plate and electric heating elements above said plate in heat exchange relation to said plate, and grouped toward one end thereof, an inner housing surrounding said hotplate and spaced from the upper and lower surfaces thereof, an outer housing surrounding said inner housing and spaced therefrom, heat insulating material 6 between said inner and outer housing, the end of said inner housing adjacent the grouped heating elements being open and the like end of said outer housing having a slot in front of said open end, a flat slide formed of a refractory composition of low heat conductivity movable into said inner housing and spaced below said hotplate and projecting through said slot in said outer housing.

2. A uniform temperature fusing device for fusing resinous powder images onto a temperature sensitive sheet material, the powder having a fusing temperature only slightly below the temperature of sensitivity of the sheet material comprising, in combination, a hotplate comprising a metal plate and electric heating elem-ents above said plate in heat exchange relation to said plate, and grouped toward one end thereof, an inner housing surrounding said hotplate and spaced from the upper and lower surfaces thereof, an outer housing surrounding said inner housing and spaced therefrom, heat insulating material between said inner and outer housing, the end of said inner housing adjacent the grouped heating elements being @Den and the like end of said outer housing havingI a slot in front of said open end, a flat slide movable into said inner housing and spaced below said hotplate and projecting through said sl-ot in said outer housing, a handle on the outer end of said slide and a paper lift bar positioned against the top face of said slide and pivot means provided on said slide at the outer end thereof to raise said bar away from said slide.

3. A uniform temperature device for fusing powder images on the surface of temperature sensitive sheet material, the powder having a fusing temperature only slightly below the temperature of sensitivity of the sheet material, th-e device comprising a horizontal hotplate with at least one heating element positioned toward the front thereof, a slide plate, a supporting and heat insulating housing enclosing said hotplate and provided with a horizontal slide slot and guide means for inserting said slide plate underneath said hotplate, said slide plate being provided with an enlarged outer end for closing said slot when said slide is inserted, a handle on said enlarged outer end, and a lift bar resting against the face of said slide plate and pivoted in said enlarged outer end with a portion thereof extending beyond said outer end to afford a means for manually turning said lift bar in said pivot to raise said bar away from the surface of said slide plate.

, EDWARD R. SABEL.

FRANK I. GALBRECHT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,574,056 Powers Feb. 23, 1926 1,596,214 OBrien Aug. 17, 1926 1,706,017 Wiegand Mar. 19, 1929 1,798,763 Smith Mar. 31, 1931 2,031,995 Yost Feb. 25, 1936 2,187,760 Sherman Jan. 23, 1940 2,223,034 Fuchs Nov. 26, 1940 2,297,691 Carlson Oct. 6, 1942 FOREIGN PATENTS Number Country Date 263,745 Great Britain July `2l, 1927 

